Communication between a transmitter and a receiver is only effective within a predetermined radius R. When data communication is required between moving participants each of whom is provided with a suitable transmitter and receiver, each participant would receive data transmitted by any other participant within a radius R thereof unless, of course, steps were taken to prevent this. Whilst it is possible to allocate different transmission frequencies to each of the participants, this is not feasible when completely reciprocal data communication is required between all of the participants. Such reciprocal data communication is a requirement, for example, in military aircraft where a limited number of pilots must be able to maintain contact with other friendly pilots all of whom must, therefore, transmit and receive data at the same network.
In such data communication, it is clearly an imperative that a pilot receive data from only one transmitter at any given time in order to avoid the collision which would result from more than one transmission being received simultaneously. At its simplest, this desideratum can always be achieved by allocating time slices to each of the participants so that only one can transmit during any given time slice. According to such an approach, each participant transmits data during his time slice only and all participants within a radius R of the transmitting participant will receive the transmitted data.
U.S. Pat. No. 5,396,644 (Tzidon et al.) discloses a method and system of communicating between moving participants such that each participant is provided with a first time slice and a respective priority listing containing the name of each participant once only, each participant thus having the top priority for one first time slice only. Also allocated to each participant is a second time slice during which he must transmit his identity as well as the identities of all his near neighbors within a radius R thereof. For each participant A there is stored the identity of all near neighbors B(A) and all far neighbors C(A) being within a radius R of his near neighbors B(A) and who are not also near neighbors B(A) of A. During each first time slice, any participant having a higher priority for the respective first time slice than all of his near and far neighbors may transmit data including the identities of at least those of his near neighbors who became near neighbors since his previous transmission. During each second time slice, non-transmitting participants update their respective list of near neighbors in respect of a transmitting participant according to whether his transmission is, or is not, received by them.
The present invention takes the above-mentioned concept further and provides several enhancements and novel features as is described herein.